1. Technical Field
Embodiments of the present invention generally relate to a sheet feeder and an image forming apparatus, such as a copier, a facsimile machine, a printer, a plotter, and a multifunction peripheral having at least two of copying, printing, facsimile transmission, plotting, and scanning capabilities; or an inkjet recording device, that includes the sheet feeder.
2. Description of the Related Art
One of qualities of image forming apparatuses such as copiers, facsimile machines, and printers, is sheet conveyance quality. Currently, various types of sheets (i.e., recording media) are used in image forming apparatuses, and there is a demand for quality improvement in sheet feeding and separation. For high-quality sheet feeding and separation, RF (Roller Friction) type sheet feeding and FRR (Feed and Reverse Roller) type sheet feeding are known.
Although RF type and FRR type sheet feeding are capable of high quality sheet feeding and separation, the cost is higher and reduction in size is difficult. By contrast, sheet feeders using a friction pad (hereinafter “friction pad type”) is known as relatively inexpensive and compact.
In the friction pad type, a table to which a friction pad (i.e., a separation pad) is attached is disposed beneath a feeding roller. In the friction pad type, a sheet set out by the feeding roller is caused to contact the separation pad to inhibit feeding of multiple sheets at a time (multifeed) by friction between the sheet and the separation pad. Then, only the top sheet in contact with the feeding roller is separated from the rest and transported to an image forming unit.
The separation pad is made of a material smaller in friction coefficient than a material of the feeding roller. For example, natural rubber, cork, leather, urethane, synthetic rubber, or the like is used singly.